• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 82 subscribers
  • Views 1127 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

about MATH_EMAVG problem in Digital Power Library

Yang Meng-Chu
Prodigy 150 points

Other Parts Discussed in Thread: CONTROLSUITE

Dear all,

 

I'm confuse about coeffieient of Multiplier, the user guid tell me the Multiplier is the weighting factor used in exponential moving average.

We use MATH_EMAVG marco to get the average value of AC Line, the Multiplier value for this can be estimated through Time Domain as below:

Our sampling at 100KHz and the input AC signal is 60Hz. as the average of the rectified sine signal is desired the effective frequency of the signal being averaged is 120Hz. the implies that (100KHz/120)=833 samples in one half sine. so we can get Multiplier for 1/833=0.0012.

but why user guid calculation is 1/3332=0.003 and tell me AC line average a value of 4000 samples (it averages roughly over 4 sine halves) in DPLib.pdf page 120?

Another, in Frequency Domain section, why the cut-off frequency is 5Hz? if our Frequency use 50Hz, what's the cut-off frequency?

 

  • 0
    TI__Mastermind 43730 points

    Yang Meng Chu,

    The emavg block is not really meant for measuring the average of the sine wave, please look at the use of sineanalyzer in

    controlSUITE\development_kits\BLPFC_v1.0\BLPFC

    where a C block called SineAnalyzer is used to measure the average, the source for the block is found here,

    controlSUITE\libs\app_libs\digital_power\f2803x_v3.2\include

    when using the EMAVG you would have to use average over multiple AC cycles, this makes the response of the outer voltage loop slow. That's why sinealayzer block is preferred for cycle by cycle average.

    Cut off is chosen as 5Hz as you are measuring the average of the AC signal not the AC signal itself. The Average is a DC quantity. 

    Hope this helps

    Manish Bhardwaj 

     

  • 0 in reply to Manish Bhardwaj
    Prodigy 150 points

    Thanks for you reply.

    Actual I use this EMAVG in HVPFC, so you mean the EMAVG is reference value, if we want to know real average of AC line, I need to use sineanalyzer to get for precise.

    But that need use two ISR, one is PFC_ISR, one is Sineanalyzer_ISR, Did I effect our performance in HVPFC?

     

    About cut-off chosen, what's the method that can let me to get DC quanity?

  • 0 in reply to Yang Meng-Chu
    TI__Mastermind 43730 points

    thats's why the cutt off is chosen as 5Hz close to 0Hz that is DC for the average